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A. K. Khatua , S. Chakrabarti , N. Malllck

Abstract

The sweet fragrance of Sal flower attracts the varied groups of insects. In the present study , the insects visiting the Sal flowers during blooming period (i.e. March) were studied for two consecutive years. (1985-86) during morning , noon and afternoon periods in the dry deciduous natural Sal forests ofArabari , Midnapore , West Bengal , India. As many as 84 different types of species representing 44 families under 7 orders viz. , Coleoptera , Diptera , Hemiptera , Homoptera , Hymenoptera , Lepidoptera and Thysanoptera were collected. Insects were identified. Their abundance , varieties and activities were studied. Availability of the insect per hour were recorded. Percentage of different groups were calcuated and diversity indices (D' values) of the species were analyzed. In the general the '0' values were highest in the morning followed by afternoon and noon. From the study it clearly appears that Sal flowers are entomophilious in nature and most active pollinators are some dipteran flies an4 bees. However , almost all the insects appear on flower heads , play some role in this pollen transfer process. And different pollinators exert varied selective forces as a result of their effectiveness in pollen transport system.

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A. K. Khatua

Abstract

Seeds of Sal (Shorea robusta) are an industrially important seasonal forest product of India. These seeds on the forest floor as well as in the godown are often found to be infested by the weevil Sitophilus rugicollis Casey (Coleoptera: Curculionidae). Rates of seed infestation were studied from the Sal seeds collected from different forest floors in Midnapore, West Bengal, India during April to July to 1983-85. The rate of Sal seed infestation was very low (10.13 ± 3.77%) in April. The incidence rose steeply from May-July (24.98 ± 5.47%; 60.51 ± 9.76% and 97.70 ± 1.55% in May, June and July respectively). At the end of July the maximum number of seeds on the forest floor were infested by the weevil. The rate of adult emergence usually shows a little higher trend under laboratory conditions (7.65 ± 1.68 per seed) then under natural conditions (6.03 ± 1.69 per seed). Thus, even a small cluster of seed is capable of producing a considerable weevil population either in field or in godown. And due to their higher intrinsic capacity of damage, the weevil causes a tremendous economic loss in the area during each and every year.

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A. K. Khatua

Abstract

Studies on occurrence and sea sonal fluctuation of six important lepidopterous defoliators of Sal viz., Chatra grisea, Trabala vishnou, Lymantria ampla, Selepa celtis, Stictoptera cuculloides and Tetridia caletoralis in Godapiasal forest area of Midnapore, reveal their maximum availability during October, January, July, April, May and April respectively. Seasonal indices of the respective species are computed accordingly. Nature of damage by the respective caterpillars and their natural enemies are also studied. Defoliation in this dry deciduous forest is maximum during pre-monsoon period by T. caletoralis, during monsoon by L. ampla, during post-monsoon period by C. grisea and during winter period by T. vishnou.

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A. K. Khatua , Samiran Chakrabarti

Abstract

Shorea robusta is an important tropical timber. Seeds of this plant are economically important and infested by a weevil, Sitophilus (Calandra) rugicollis Casey. The insect hibernates in adult stage within soil or decomposed ischolar_mains under the soil during September to May. They are most abundant during May-June when sal seeds become mature and fall on the forest floor. No alternate host of this insect is recorded in the area. Life history and seasonal activity of this pest has been studied and discussed in this paper.

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